Police have charged a man over the death of six-month-old Serenity Jay Scott in Ngaruawahia, north of Hamilton.
Serenity died last April of traumatic brain injuries.
A 21-year-old man was arrested on Sunday and charged with her murder, Detective Senior Sergeant Mark Greene says.
He will appear in Hamilton District Court on Monday.
"To get to the point where we have sufficient evidence to bring this matter before the courts highlights the hard work and long hours put in by an investigation team who always remained focused on doing what is right for a little girl, whose life ended so tragically."
The arrest was also testament to the local community, which had made it clear it would not tolerate violence against children, Mr Greene said.
The strong relationship between Waikato police and Child, Youth and Family was also invaluable to the investigation of the nine-month-old homicide.
The case was a good example of how seriously police took child abuse, and he urged anyone with knowledge of abuse going on to speak up, Mr Greene said.
"It's a case of see something do something, and as a community we can make a difference. Look after your kids, love them and protect them. "
The arrest was a milestone but police investigations into Serenity's death continued, he said.
Serenity was found unresponsive at the Ngaruawahia house where she lived with her mother Chelsea Scott, then aged 21, Ms Scott's boyfriend Matthew Ellery, and her brother, Drew Scott.
She was taken to Auckland's Starship Hospital, where she died two days later.
NZN